Windermere town and Bowness-on-Windermere are about a mile apart, mostly downhill from the station to the lake. The walk takes 20 minutes; the local buses (599 and 555) connect them every few minutes in season and are cheap.
For the lake itself, Windermere Lake Cruises runs scheduled boats year-round from Bowness pier to Ambleside, Lakeside (for the South Lakes Steam Railway), and Brockhole. A day pass lets you hop on and off. The chain ferry across the lake from Ferry Nab links the eastern shore to the western side at Hawkshead — cars, bikes, and foot passengers all carried, runs every 20 minutes.
A car is useful for reaching outlying sights but parking is a constant headache. Hire bikes from Country Lanes Cycle Centre at Windermere station; the lakeshore lanes are quiet and pretty for cyclists.